There exists an extensive market for injury protection-related athletic gear, much of which currently employs foam-based padding for joints (elbow and knees) or common athletic tape for joint-related twisting. The Centers for Disease Control (CDC) provide data relative to the numerous recreational sports injuries (totally more than 10 million episodes each year with costs approaching $300 billion) in the form of non-lethal blunt-force trauma (i.e. being struck with balls, sticks, bats, clubs, other players, hard surfaces, or otherwise damage-inducing materials), causing bruises, abrasions, sprains, breaks, or other traumatic injuries. There are also inertial injuries that occur as a result of changes of direction imposed by the body not involving an impact (e.g., non-contact injury; twisting, torsion-based injury).
Sports-associated injuries, especially to the lower extremities, may cause immediate damage, ultimately limiting physical activity and causing long-term problems associated with mobility. Ankles and knees are very susceptible to contact and non-contact injuries as a result of the inherent unsteadiness within the joints themselves. While the human body is certainly capable of absorbing and dispersing blunt-force trauma, significant injuries are the consequence of considerable forces.
Shear thickening fluids, (STFs), also known as Non-Newtonian fluids and/or dilatants, are generally comprised of a suspension media (typically polymer-based) and inorganic colloidal particles of relatively uniform size. Normally, the STF is able to flow easily when force or high velocity is not applied. Under increased stress or strain at higher velocities or with elevated pressure, the STF rapidly stiffens or solidifies in response to the increased force as a result of higher viscosity and/or the alignment of the spherical particles within the suspension media. Importantly, this stiffening effect is a dynamic process with a rapid “on and off rate”, making the material housing the STF both elastic and resilient.